RAPID LIGHT-INDUCED-CHANGES IN CELL FLUORESCENCE AND IN XANTHOPHYLL-CYCLE PIGMENTS OF ALEXANDRIUM-EXCAVATUM (DINOPHYCEAE) AND THALASSIOSIRA-PSEUDONANA (BACILLARIOPHYCEAE) - A PHOTO-PROTECTION MECHANISM
RAPID LIGHT-INDUCED-CHANGES IN CELL FLUORESCENCE AND IN XANTHOPHYLL-CYCLE PIGMENTS OF ALEXANDRIUM-EXCAVATUM (DINOPHYCEAE) AND THALASSIOSIRA-PSEUDONANA (BACILLARIOPHYCEAE) - A PHOTO-PROTECTION MECHANISM
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DOI：
10.3354/meps076185
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发表时间：
1991-09-01
影响因子：
2.5
通讯作者：
VIGNAULT, C
中科院分区：
文献类型：
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作者：
DEMERS, S;ROY, S;VIGNAULT, C
在体内叶绿素a（chl a）荧光每个细胞的研究，用流式细胞仪测量，和培养的植物光合细胞的色素组成表明，叶黄素循环起着防止光抑制损伤光合机构的作用。测试了两个物种：Alexandrum unculatum（甲藻纲）和Thalassiosira damana（硅藻纲）。细胞在3种适应光条件下生长：连续低光（50 μ mol光子m-2 s-1）、连续强光（500 μ mol光子m-2 s-1）和波动光（50、1000和50 μ mol光子m-2 s-1;循环频率= 1 h-1）。当细胞突然受到短时间（30 ~ 60分钟）连续高光强（1000 μ mol光子m-2 s-1）照射时，每个细胞信号的体内荧光时间进程显示荧光迅速减少。该降低为初始荧光水平的约50%至65%。当实验灯关闭时，荧光恢复到通常接近其初始值的水平。与这些快速荧光降低同时，无环氧基颜料硅藻黄质的浓度在暴露于强光时以牺牲其母体化合物硅藻黄质为代价而增加。当灯关掉时，这个过程就颠倒过来了。3种驯化条件的比较表明，荧光猝灭与单位叶绿素a中的硅藻黄质浓度有关，在强光和弱光驯化的细胞中也是如此。除了色素的快速可逆反应外，高光适应的细胞即使在黑暗中保持1至2小时也能保持硅藻黄质的正浓度。低光适应的细胞在黑暗中失去了它们的硅藻黄质部分。因此，驯化控制着细胞中叶黄素循环色素的长期积累，但它似乎不依赖于与荧光猝灭有关的叶黄素循环的快速反应。这两个物种，但特别是A。在凹穴的情况下，由于光暴露并伴随着叶黄素色素变化而导致的荧光猝灭表明，在色素床中发生了非辐射能量耗散，如在具有活性叶黄素循环的高等植物中。这种机制可能使藻类能够适应光场的快速变化，并使细胞能够建立长期的光保护机制，例如调节色素含量和组成。
Studies of in vivo chlorophyll a (chl a) fluorescence per cell, measured with a flow cytometer, and the pigment composition of cultured phytoplanktonic cells suggested that the xanthophyll cycle plays a role in the prevention of photoinhibitory damage to the photosynthetic apparatus. Two species were tested: Alexandrium excavatum (Dinophyceae) and Thalassiosira pseudonana (Bacillariophyceae). Cells were grown under 3 acclimation light conditions: continuous low light (50-mu-mol photons m-2 s-1), continuous high light (500-mu-mol photons m-2 s-1) and fluctuating light (50, 1000, and 50-mu-mol photons m-2 s-1; cycle frequency = 1 h-1). The time course of in vivo fluorescence per cell signal showed rapid decreases in fluorescence when cells were suddenly submitted to a continuous high light intensity (1000-mu-mol photons m-2 s-1) for short periods of time (30 to 60 min). This decrease was ca 50 to 65 % of the initial fluorescence level. When the experimental light was turned off, fluorescence returned to a level generally close to its initial value. Concurrent with these rapid fluorescence decreases, the concentration of the epoxy-free pigment diatoxanthin increased at the expense of its parent compound, diadinoxanthin, upon exposure to high light. The process reversed when the light was turned off. Comparison among the 3 acclimation conditions suggests that fluorescence quenching is related to the concentration of diatoxanthin per unit chl a in the same way for high-light- and low-light-acclimated cells. In addition to the fast, reversible reaction in pigments, the high-light-acclimated cells maintain a positive concentration of diatoxanthin even when kept in darkness for 1 to 2 h. Low-light-acclimated cells lose their diatoxanthin fraction when put in the dark. Thus acclimation controls the long-term accumulation of the xanthophyll-cycle pigments in cells but it seems independent of the rapid reactions of the xanthophyll cycle that are related to fluorescence quenching. For both species, but particularly for A. excavatum, fluorescence quenching, resulting from light exposure and accompanied by xanthophyll pigment changes, suggests that non-radiative energy dissipation is taking place in the pigment bed, as in higher plants possessing an active xanthophyll cycle. This mechanism potentially allows algae to accomodate to rapid changes in the light field and permits cells to build up longer-term mechanisms of photoprotection such as regulation of pigment content and composition.